1. Field of the Invention
The present invention relates to the field of movable object location systems generally and more particularly to a system utilizing an advanced radio frequency detection method for detecting the location of golf balls.
2. Description of the Prior Art
Golf is an increasingly popular game typically played in teams of two or four. The course of play typically consists of nine or eighteen holes with each hole consisting of a length of course a few hundred yards long beginning with a xe2x80x9cteexe2x80x9d and ending in a xe2x80x9cgreenxe2x80x9d which contains the xe2x80x9cholexe2x80x9d. Golf is controlled by a number of intricate rules one of which requires a player who loses a ball to take a penalty stroke which harms that player""s score. Thus, players are understandably reluctant to take a penalty stroke without making a time consuming effort to find the lost ball. However, since only one team can play a xe2x80x9cholexe2x80x9d at any given time, the number of teams on the course and the speed of play is limited to that of the slowest moving team. If one team stops play because a particular player is searching for a lost ball, all of the teams behind them are forced to stop play as well. This directly conflicts with the desire of teams waiting to continue play and with the financial incentives of golf course mangers who prefer to have teams moving at swift pace through the course. Because of these conflicting goals many courses have adopted a five minute search rule. If a ball cannot be located after five minutes a player is forced to take a penalty stroke. Most commonly golf balls are lost during the course of play because the ball lands in a particularly overgrown area of the course. The loss can occur even though the ball was visible during its entire flight and the approximate region in which the ball landed is known. Thus, there have been many attempts at developing a device or method for finding a lost golf ball.
Early attempts at developing a golf ball location device have included U.S. Pat. No. 1,583,721, issued to Kane, May 4, 1926. Kane disclosed a smoke signaling device wherein a golf ball emitted a smoke signal prior to being hit. The golfer, after lighting a fuse, could track his ball by watching the smoke trial left in the air. Another early attempt was U.S. Pat. No. 1,620,290, issued to Rubin, Mar. 8, 1927. This device comprised a golf ball which contained a spring powered bell. Prior to hitting the ball, the golfer would wind the spring which would start the bell ringing. A more recent suggestion is British Patent No. 1,121,630, issued to Pedrick, Jul. 31, 1968. Pedrick suggested manufacturing a golf ball with a radioactive core. The golf ball when lost could then be located by means of a gas filled counting tube to detect the radioactive rays such as a Geiger counter. These early attempts are provided as an illustration of the long felt and as yet unmet need for an effective method of locating a lost golf ball.
The modern prior art concepts can be divided into two categories, electronic golf balls and remote sensing systems. In the electronic golf ball category there are generally two approaches, golf balls incorporating battery powered radio transmitters and golf balls incorporating battery powered audio beepers. An example of the radio transmitter approach is U.S. Pat. No. 3,782,730 entitled xe2x80x9cGolf Ballxe2x80x9d, issued to Horchler, Jan. 1, 1974. This patent discloses a miniature, battery powered, radio transmitter enclosed within a golf ball. Horchler uses a small mercury cell, similar to a watch or camera battery, which powers a squegging oscillator type transmitter circuit. The battery and circuit are encapsulated within the golf ball. There are several inherent problems with the Horchler device. One problem is that the battery being encapsulated within the golf ball cannot be replaced. Therefore, when the battery fails a relatively expensive golf ball must be thrown away. It is also questionable whether a small mercury cell could supply sufficient power to generate a transmitter signal providing sufficient range to be practical during actual play. Further there is reason to doubt whether the active components of the Horchler device could survive the repetitive shock loads transmitted to a golf ball during a typical game.
An example of the audio beeper approach to locating a lost golf ball is U.S. Pat. No. 5,112,055 entitled xe2x80x9cGolf Ball Including Sound Emitting Meansxe2x80x9d, issued to Barnhill, May 12, 1992. The Barnhill golf ball contains a battery operated audio beeper circuit which includes a latch type switch. Upon being struck, the force of the blow imparted to the ball closes the switch causing the ball to emit an audible beep. By means of the continuous beeping the golfer may locate his ball. The beeper is turned off by pressing a golf tee through a hole inside the golf ball and thereby resetting the latch switch to the off position. While an interesting idea. Barnhill has numerous potential drawbacks. If the beeper signal is loud enough to allow a golfer to locate a lost ball from a distance of one hundred or more yards it is likely to prove annoying to other golfers. On the other hand if the beeper is quiet enough not annoy other golfers it is not likely to be loud enough to allow the golfer to find the lost ball. Further, as with Horchler, the life of the Barnhill golf ball is limited to the life of the battery and once again it is questionable whether the active components can withstand the repetitive shock loads imparted to a golf ball during the course of play.
Of the remote sensing methods for locating golf balls disclosed in the prior art there are three main types, proximity sensors, optical systems based on charge coupled device (CCD) sensors, and radar type systems. An example of the proximity sensor approach is U.S. Pat. No. 4,660,039, entitled xe2x80x9cSystem For Locating A Sport Objectxe2x80x9d, issued to Barricks et al., Apr. 21, 1987. Barricks discloses a low frequency radio transmitter and a golf ball wherein strips of conductive material are placed around the perimeter of the ball. Barricks operates on the well known principle that when an electromagnetic (EM) field comes into contact with a conductor an electrical current commonly referred to as an xe2x80x9ceddy currentxe2x80x9d is induced in the conductor. When the EM field first contacts the conductor, the induced current causes the transmitter to see an increased load or power drain. A proximity sensor included with the transmitter senses the increased power drain and thereby the presence of the ball can be inferred. The primary disadvantage of this approach is that proximity to a conductor produces only a slight power drain on a transmitter. Therefore, even very sensitive proximity sensors require that the transmitter and conductor be in close spacial relation in order to generate a detectable differential in power drain. In industrial applications proximity sensors have an effective range of a few inches to about two feet. In actual practice, a golf ball locator based on a proximity sensor approach would likely be limited to a similarly short effective range.
An example of the CCD approach is U.S. Pat. No. 5.662,533, entitled xe2x80x9cGolf Ball Locator Apparatusxe2x80x9d, issued to Chadwell, Sep. 2, 1997. Chadwell teaches a system comprising a hand held infrared light source which includes an array of charge coupled devices designed to be particularly sensitive to infrared light, a golf ball coated with a clear coating that is formulated to be highly reflective of infrared light, and circuitry capable of detecting reflected infrared light. One disadvantage of the Chadwell method is that infrared radiation will not penetrate foliage. Thus if the lost golf ball is obscured by grass, leaves, brush or other type of foliage the detection system taught by Chadwell will not be effective.
An example of the radar approach to golf ball detection is U.S. Pat. No. 5,662,534, entitled xe2x80x9cGolf Ball Finding Systemxe2x80x9d, issued to Kroll et al., Sep. 2, 1997. The system taught by Kroll uses radar principles well known to those skilled in the art. Kroll discloses a hand held radar transponder and a four quadrant corner reflector encapsulated within a golf ball. Kroll teaches that radar waves impinging on the reflector at an oblique angle will, after multiple reflections within a quadrant, be reflected directly back to the radar source. Kroll estimates, by calculation, that to locate a golf ball by radar means using the disclosed four quadrant reflector a minimum transmitter frequency of 15 Ghz would be required. Kroll further calculates that an effective range of 500 feet could be obtained at this frequency and that the transponder could be powered by ordinary dry cell batteries xe2x80x9cas is done with a flashlight.xe2x80x9d While detection of a golf ball by radar means is quite feasible, it is highly questionable whether a transmitter operating at 15 Ghz could be powered by a sufficiently small number of ordinary dry cell batteries such that the device could be hand held. Further, it is questionable whether an impinging radar wave striking the reflector at an oblique angle will be reflected directly back to the transmitter as is required for the Kroll device to operate. In addition, a four quadrant corner reflector would cut through the core of the golf ball severing it into fourths, thereby ruining its flight characteristics.
Although the prior art discloses a multitude of systems for locating a lost golf ball, all of the methods taught possess certain drawbacks. Thus, it is clear that there remains room for improvement. What is needed therefore is a remote sensing golf ball location system of sufficiently low power consumption to be light weight and portable, and preferably hand held. In addition, such a system should not compromise the integrity of the golf ball bounce and flight characteristics. Further, such a system should possess sufficient range to be of practical utility and such a system should be able to locate a golf ball regardless of the ball""s physical orientation on the course or whether the ball is obscured by foliage.
The present invention provides a system which may be employed for locating lost golf balls which includes a golf ball that incorporates an array of passive transponders and a radio frequency (xe2x80x9cRFxe2x80x9d) transmitter/receiver capable of energizing the passive array and of detecting a signal emitted by the array. Each passive transponder is a capacitively loaded flat-loop inductor of predetermined configuration. The array comprises three flat-loop inductors arranged in a predetermined spatial relationship within the interior of a golf ball. Each flat-loop inductor functions as a tuned LC circuit that is charged by the RF transmitter/receiver and emits a radio frequency signal, detectable by the transmitter/receiver, for a finite period of time after the RF transmitter/receiver is turned off.
It should be noted that the present invention does not utilize radar principles. The amount of RF energy emitted by the passive transponders is orders of magnitude greater than that which would be reflected back from the conductive surfaces contained within the golf ball by an impinging electromagnetic wave. With our device, RF energy is emitted from the surface of the golf ball for hundreds of nanoseconds after the RF energy from the transmitter is no longer striking the surface of the ball. Therefore, the emissions are not radar, since radar emissions from a target stop as soon as the energy from the radar transmitter is shut off.
The present invention possesses several advantages over the prior art. The passive array incorporated in the golf ball of the present invention contains no conventional electronic components and is therefore impervious to the impact loading produced by hitting a golf ball during the normal course of play. Further, the signal emitted by the passive array is omni-directional and therefore detectable by the transmitter/receiver regardless of the orientation of the golf ball on the course. Also, the present invention can detect a golf ball incorporating the passive array regardless of whether the ball is obscured by foliage. In addition, the RF transmitter/receiver of the present invention possesses sufficient transmitter power to provide an effective range of at least 100 feet, yet power consumption is sufficiently low such that the transponder/receiver can be operated with ordinary dry cell batteries. Other features and advantages of the invention will become apparent from the following detailed description.